class_docstr: Unit tests for the LangChain wrapper LLM class
code: def test_langchain_model_call(self, langchain_llm, prompt):
      langchain_wrapper = LangchainLLM(langchain_llm)
  
      assert (
          langchain_wrapper.call(instruction=prompt, suffix="!")
          == "Custom response"
      )
  
file_path: pandas-ai/tests/llms/test_langchain_llm.py
imports: from langchain.llms import OpenAI
  import pytest
  from pandasai.llm import LangchainLLM
  from pandasai.prompts import AbstractPrompt
  from unittest.mock import Mock
label_desc: Use image node_id 4 for calling the TestLangchainLLM obj's underlying member method code with example usage: obj.test_langchain_model_call(langchain_llm, prompt) without return types